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Abstract:

A battery backup unit (BBU) includes a housing, at least one battery
compartment in the housing with an output terminal, a DC input, a DC
output, a path from the DC input to the DC output, circuitry for
selectively connecting the output terminal to the path, which circuitry
includes a switch, and a controller configured to detect a condition of
the path and selectively control the switch to connect the output
terminal to the path when the condition is detected, the BBU being
incapable of charging batteries in the at least one battery compartment.
The path from the DC input to the DC output may include a DC/DC step up
converter to help maintain a constant output voltage.

Claims:

1. A battery backup unit (BBU) comprising: a housing; at least one
battery compartment in the housing including an output terminal; at least
one DC input; a DC output; a path from the at least one DC input to the
DC output; circuitry connecting the output terminal to the path and
including a switch for selectively connecting the output terminal to the
path, the circuitry precluding current flow from the at least one DC
input to the output terminal; and a controller configured to detect a
condition of said path and to selectively control said switch when said
condition is detected.

2. The BBU of claim 1 wherein said condition is a voltage level on said
path.

3. The BBU of claim 1, wherein said circuitry includes a DC/DC converter
between the output terminal and the path.

5. The BBU of claim 1 wherein said controller includes a first input
receiving a signal indicative of the presence or absence of said
condition and a first output connected to said switch.

6. The BBU of claim 1, wherein said housing includes at least one visual
indicator providing a first visual indication when the condition is
detected and a second visual indication different than said first visual
indication when the condition is not detected.

7. The BBU of claim 1 including at least one visual indicator providing a
visual indication of a remaining life of a battery in said at least one
battery compartment.

8. The BBU of claim 1 including a voltage regulator connected to the path
and to an input of the controller.

9. The BBU of claim 1, wherein said controller is configured to open said
switch when an output from said output terminal is between a first level
and a second level.

10. The BBU of claim 1 including a data port and a conductor connecting
said data port to said controller.

11. The BBU of claim 1 including at least one battery removably mounted
in said at least one battery compartment.

12. The BBU of claim 1 including: a DC/DC converter between the output
terminal and the path, wherein said controller includes a first input
receiving a signal indicative of the presence or absence of a first level
of DC power on said path and a first output connected to said switch, and
a voltage regulator connected between the path and a regulator input of
the controller.

13. The BBU of claim 12, including a data port and a conductor connecting
said data port to said controller, wherein said DC/DC converter comprises
a step-up converter, wherein said controller is configured to open said
switch when an output from said output terminal is between a first level
and a second level and wherein said housing includes at least one visual
indicator providing a first visual indication when the first level of DC
power is present, a second visual indication different than said first
visual indication when said first level of DC power is absent and a third
visual indication of remaining life of a battery in said at least one
battery compartment.

14. A battery backup unit (BBU) comprising: a housing; at least one
battery compartment in the housing including an output terminal; a DC
input; a DC output; a path from the DC input to the DC output; circuitry
for selectively connecting the output terminal to the path and including
a switch; and a controller configured to detect a condition of said path
and to selectively control said switch to connect said output terminal to
said path when said condition is detected, wherein said BBU is incapable
of charging batteries in said at least one battery compartment.

15. The BBU of claim 14 wherein said condition comprises a voltage of
said path.

16. The BBU of claim 15, including a DC/DC converter between the output
terminal and the path, wherein said controller includes a path condition
input receiving a signal when said condition is detected and a first
output connected to said switch, and a voltage regulator connected
between the path and a regulator input of the controller.

17. The BBU of claim 16, including a data port and a conductor connecting
said data port to a data input of said controller, wherein said DC/DC
converter comprises a step-up converter, and wherein said housing
includes at least one visual indicator providing a first visual
indication when the condition is detected, a second visual indication
different than said first visual indication when the condition is not
detected and a third visual indication of a remaining life of a battery
in said at least one battery compartment.

18. A battery backup unit (BBU) comprising: a housing; at least one
battery compartment in the housing including a battery terminal; a DC
input; a DC output; a DC path from the DC input to the DC output; and
control means for controlling current flow at said battery terminal and
circuitry means for selectively connecting said battery terminal to said
path, said control means including a controller for detecting a condition
of said path and for controlling said circuitry means to selectively
connect said battery terminal to said path when said condition is
detected.

19. The BBU of claim 18, wherein said condition comprises a voltage level
on said path.

20. The BBU of claim 18, including at least one battery removably mounted
in the at least one battery compartment, wherein said circuitry means
precludes the recharging of said at least one battery while said at least
one battery is mounted in said at least one battery compartment.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional
Patent Application No. 61/372,131 filed Aug. 10, 2010, the entire
contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention is directed to a battery backup unit (BBU)
having a DC input, a DC output, a compartment for removably receiving a
plurality of batteries and a controller for connecting the batteries to
the DC output when no current is detected at the DC input and, more
specifically, toward a BBU having a DC input, a DC output, a compartment
for removably receiving a plurality of batteries and a controller for
connecting the batteries to the DC output when no current is detected at
the DC input, wherein the BBU is incapable of charging the batteries in
the battery compartment.

BACKGROUND OF THE INVENTION

[0003] In conventional telephone systems, power and data are provided over
wires that connect a customer's home to a telephone central office. In
newer telephone systems, data may be provided over an optical fiber that
terminates at an optical network unit (ONU) or network interface unit
(NIU) located at a customer's home or business. These systems are
referred to as fiber-to-the-home (FTTH) systems. Power cannot be
transmitted over the optical fiber, and therefore, power for operating
the ONU and its internal laser and optical/electric converters is
generally provided from the customer premises via a DC converter
connected to an AC power source (e.g., a wall outlet) at the customer
premises. In the event of a power outage at the customer premises,
telephone service in a FTTH system will be lost unless backup power is
provided. However, most customer locations do not have a source of backup
power.

[0004] To address this problem, it is known to provide a battery backup
unit (BBU) at the subscriber location that provides power to the ONU in
the event of a power failure. Traditional backup systems contain an AC/DC
converter to power the ONU while power is available, and they also
provide power to a charging system that keeps a battery system charged
for use when power is interrupted. When main power is lost, the BBU
switches to the battery system which then powers the ONU. When the backup
battery is depleted, service is lost until the main power returns.

[0005] To make the BBU easy to use for a customer, the battery is usually
packaged in a custom plastic enclosure with an integrated electrical
connector. The battery pack is then easily handled and put into or
removed from the BBU. In addition, the battery pack recharges while
connected to AC power so that a customer does not need to maintain or
monitor the charge on the battery.

[0006] There are several drawbacks to this approach to providing backup
power. The first is the complexity of charging and maintaining a charge
on a battery. The correct voltages, currents, charge durations, and
charge frequencies are highly dependent on the battery technology used
(lithium ion, nickel cadmium, etc.), and even within a given technology,
these characteristics are dependent on the composition of the battery. As
a result, a charger must either be custom tuned in the factory for a
particular battery type and composition, or it must be field adaptable to
accommodate different batteries. In addition, in either scenario, if new
battery technology is developed, even if it has the same voltage and
current characteristics, its charging requirements may not be
accommodated by the charger. It therefore may be necessary to redesign or
field-upgrade the BBU when new battery technology is developed.

[0007] Custom battery packs are beneficial for ease of customer use, but
customization also means that these battery packs may not be readily
available at retail outlets. As a result, in the event of an outage that
exceeds the battery backup duration, or when the battery system fails
during an outage, a customer will not be able to maintain service because
there is no way to readily procure another battery. A customer might own
a second battery pack, but even that will not help if the charge on that
second battery pack is not maintained.

[0008] Conventional BBU's also have an integral power supply which takes
in an AC voltage and converts it to DC. While needed for the backup
system to operate, this function is redundant in many FTTH systems since
ONU's generally have their own power supplies. When battery backup is
added to the ONU, the existing power supply is removed and the BBU is
inserted. While the removed power supply could be used as a spare for an
ONU without a BBU, in general it will be an unnecessary cost addition for
the BBU.

[0009] In addition, the service provider is generally responsible for the
safety of the BBU. Some of the custom batteries used in BBU's are
susceptible to fire and/or explosion under certain conditions, and BBU's
with rechargeable batteries make safety assurance more complex. The
service provider may also need to store a large number of battery packs
for use in new installations and may be required to provide safe disposal
facilities for exhausted battery packs. Often this means additional costs
for safety elements/features in the system and testing for safety
approval from bodies such as Underwriter Laboratories (UL). It would
therefore be desirable to provide a BBU for an ONU that does not suffer
from the aforementioned shortcomings.

SUMMARY OF THE INVENTION

[0010] These problems and others are addressed by embodiments of the
present invention, a first aspect of which comprises a battery backup
unit (BBU) that includes a housing and at least one battery compartment
in the housing that has an output terminal. The BBU further includes at
least one DC input, a DC output, a path from the at least one DC input to
the DC output, and circuitry connecting the output terminal to the path
which circuitry includes a switch for selectively connecting the output
terminal to the path. The circuitry precludes current flow from the at
least one DC input to the output terminal, and a controller is provided
to detect a condition of the path and to selectively control the switch
when the condition is detected.

[0011] Another aspect of the invention comprises a BBU that has a housing
and at least one battery compartment in the housing which has an output
terminal. The BBU also includes a DC input, a DC output, a path from the
DC input to the DC output and circuitry for selectively connecting the
output terminal to the path, which circuitry includes a switch. A
controller is configured to detect a condition of the path and to
selectively control the switch to connect the output terminal to the path
when the condition is detected, and the BBU is incapable of charging
batteries in the at least one battery compartment.

[0012] A further aspect of the invention comprises a BBU having a housing
and at least one battery compartment in the housing that includes a
battery terminal. The BBU also includes a DC input, a DC output, a DC
path from the DC input to the DC output and a control mechanism for
controlling current flow at the battery terminal and a circuitry
arrangement for selectively connecting the battery terminal to the path.
The control mechanism includes a controller for detecting a condition of
the path and controlling the circuitry arrangement to selectively connect
the battery terminal to the path when the condition is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] These and other aspects and features of embodiments of the
invention will be better understood after a reading of the following
detailed description together with the attached drawings wherein:

[0014] FIG. 1 is a schematic illustration of a battery backup unit
according to the present invention connected to a network interface unit.

[0016] FIG. 3 is a circuit diagram showing exemplary circuitry for use in
a battery backup unit according to an embodiment of the present
invention.

DETAILED DESCRIPTION

[0017] The present invention now is described more fully hereinafter with
reference to the accompanying drawings, in which embodiments of the
invention are shown. This invention may, however, be embodied in many
different forms and should not be construed as limited to the embodiments
set forth herein; rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the scope
of the invention to those skilled in the art.

[0018] Like numbers refer to like elements throughout. In the figures, the
thickness of certain lines, layers, components, elements or features may
be exaggerated for clarity. Broken lines illustrate optional features or
operations unless specified otherwise.

[0019] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
invention. Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this invention
belongs. It will be further understood that terms, such as those defined
in commonly used dictionaries, should be interpreted as having a meaning
that is consistent with their meaning in the context of the specification
and relevant art and should not be interpreted in an idealized or overly
formal sense unless expressly so defined herein. Well-known functions or
constructions may not be described in detail for brevity and/or clarity.

[0020] As used herein, the singular forms "a", "an" and "the" are intended
to include the plural forms as well, unless the context clearly indicates
otherwise. It will be further understood that the terms "comprises"
and/or "comprising," when used in this specification, specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements, components,
and/or groups thereof. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed items. As used
herein, phrases such as "between X and Y" and "between about X and Y"
should be interpreted to include X and Y. As used herein, phrases such as
"between about X and Y" mean "between about X and about Y." As used
herein, phrases such as "from about X to Y" mean "from about X to about
Y."

[0021] It will be understood that when an element is referred to as being
"on", "attached" to, "connected" to, "coupled" with, "contacting", etc.,
another element, it can be directly on, attached to, connected to,
coupled with or contacting the other element or intervening elements may
also be present. In contrast, when an element is referred to as being,
for example, "directly on", "directly attached" to, "directly connected"
to, "directly coupled" with or "directly contacting" another element,
there are no intervening elements present. It will also be appreciated by
those of skill in the art that references to a structure or feature that
is disposed "adjacent" another feature may have portions that overlap or
underlie the adjacent feature.

[0022] Spatially relative terms, such as "under", "below", "lower",
"over", "upper", "lateral", "left", "right" and the like, may be used
herein for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in the
figures. It will be understood that the spatially relative terms are
intended to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures. For
example, if the device in the figures is inverted, elements described as
"under" or "beneath" other elements or features would then be oriented
"over" the other elements or features. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
descriptors of relative spatial relationships used herein interpreted
accordingly.

[0023] FIGS. 1 and 2 illustrate a battery backup unit (BBU) 10 according
to an embodiment of the present invention that includes a first DC input
12 and a second DC input 13, either one of which is connectable to a
power supply 14, and a first DC output 16 and a second DC output 17,
either one of which is connectable to a network interface unit (NIU) 18
mounted on the wall 20 of a building. The first DC input 12 and first DC
output 16 may comprise, for example F connectors while the second DC
input 13 and the second DC output 17 may comprise barrel connectors. The
first and second DC inputs 12, 13 connect to the same input node and the
first and second DC outputs 13, 17 connect to the same output node and
allow for different types of connectors to be used with the BBU 10. As
shown in FIG. 2, the BBU 10 also comprises a housing 24 having a hinged
lid 26 for selectively covering and allowing access to a first battery
compartment 28 and a second battery compartment 30. Each of the first and
second battery compartments 28, 30 includes a plurality of locations 32
for receiving a battery 33, in this case a standard AA battery, connected
to circuitry, illustrated in FIG. 3, and enclosed within housing 24. A
plurality of visual indicators 34a, 34b and 34c, which may comprise, for
example, LED's, and a data port 36 are provided on the housing 24 and
connected to the circuitry inside housing 24 as described hereafter.

[0024] FIG. 3 illustrates circuitry contained within housing 24 which may
comprise, for example elements on a circuit board interconnected by
traces or otherwise electrically coupled. The circuitry include a first
path 38 that electrically connects input 12 to output 16 and allows for a
substantially unregulated DC power flow from power supply 14 to NIU 18
via BBU 10 under normal operating conditions when DC power is provided to
input 12 by power supply 14. First battery compartment 28 is connected in
series with second battery compartment 30 by a second path 40, and second
battery compartment 30 includes an output terminal 42 connected to first
path 38 by a third path 44 which third path 44 includes a diode 46 for
preventing current flow into the second battery compartment 30, a battery
path enable switch 48 for selectively interrupting third path 44, a DC/DC
voltage regulator 50 for regulating the voltage supplied to first path 38
by the batteries 33, an EMI filter 52, a PTC element 54 and a second
diode 56.

[0025] FIG. 3 also illustrates a controller 58 for determining whether
power is being provided from input 12 to output 16 via first path 38 and
closing battery path enable switch 48 when sufficient power is not being
provided. Controller 58 may be a microcontroller unit (MCU) such as a
Silicon Labs C8051F332 MCU, with various input/output pins connected to
various circuit elements as described below. The pins of controller 58
are labeled 1-20 in FIG. 3, and these pins numbers will be referred to
hereinafter.

[0026] Pin 3 of controller 58 is connected to first path 38 by a fourth
path 60 which fourth path 60 includes a voltage regulator 62, such as a
National Semiconductor ADJ LDO LP 2951CM, for regulating the voltage
supplied to controller 58. Second path 40 between first battery
compartment 28 and second battery compartment 30 includes a node 64
connected to fourth path 60 for providing 6V DC power from the batteries
in first battery compartment 28 to voltage regulator 62 and thus to
controller 58 when adequate power is not provided from input 12.
Unregulated voltage from first path 38 is also supplied to pin 13 of
controller 58 by a mains in line 65.

[0027] Battery path enable line 66 connects battery path enable switch 48
to controller pin 16, and controller 58 controls the state of battery
path enable switch 48 by providing appropriate outputs on this line 66. A
battery 6V monitor switch 68 is connected to second path 40 and to
controller pin 15 by a battery 6V monitor enable line 70, and battery 6V
monitor switch 68 is controlled by an appropriate output of controller
pin 15. The output of battery 6V monitor switch 68 is connected to
controller pin 12 of controller 58 by battery 6V monitor output line 72
allowing controller 58 to receive as an input an indication of the
voltage being output from the batteries 33 in first battery compartment
28 and thus an indication of the charge condition of the batteries 33 in
the first battery compartment 28. A battery 12V monitor switch 74 is
connected to third path 44 and to controller pin 14 by a battery 12V
monitor enable line 76, and battery 12V monitor switch 74 is controlled
by an appropriate output of controller pin 14. The output of battery 12V
monitor switch 74 is connected to controller pin 11 of controller 58 by a
battery 12V output line 78 allowing controller 58 to receive as an input
an indication of the voltage being output from the batteries 33 in first
and second battery compartments 28, 30 and thus an indication of the
charge condition of the batteries in the first and second compartments
28, 30. When the output of the batteries 33 reaches a level greater than
zero but too low to provide adequate power to NIU 18, controller 58 opens
battery path enable switch 48 and shuts off power to the output terminal
16.

[0028] A boost reg out line 80 connects a node 82 in third path 44 between
DC/DC voltage regulator 50 and EMI filter 52 to controller pin 10, and a
post PTC out line 84 connects a node 86 between PTC element 54 and second
diode 56 to controller pin 14 to provide controller 58 with additional
information about voltage levels in the system. Controller pins 4 and 5
are connected to data port 36 by lines 88 and 90, respectively, for
allowing communication between data port 36 and controller 58. First
visual indicator 34a is connected to controller pin 20, second visual
indicator 34b is connected to controller pin 19 and third visual
indicator 34c is connected to controller pin 18, and a buzzer 92 is
connected to controller port 17 by a switch 94 so that controller 58 can
control the first, second and third visual indicators 34a, 34b, 34c and
buzzer 92 to provide information about the power source being used by the
BBU 10 and the condition of the batteries 33.

[0029] Under normal operating conditions, DC power is supplied to BBU
input 12 and output from BBU output 16 with power also being supplied to
voltage regulator 62 via fourth path 60 and to pin 13 of controller 58
via mains in line 65. The controller 58 monitors the voltage on first
path 38 via mains in line 65 and, if this voltage drops below a
predetermined level, a level consistent with the lowest expected normal
voltage from power supply 14, controller 58 closes battery path enable
switch 48 within milliseconds of the detected drop to connect output
terminal 42 of second battery compartment 30 to BBU output 16 over third
path 44 thereby providing a substantially uninterrupted power supply from
BBU output 16 even when power ceases to be supplied to first path 38 via
BBU input 12. DC/DC regulator 50, which may comprise a boost regulator,
helps maintain a constant voltage level at BBU output 16 even as the
batteries 33 discharge, and the charge level of batteries 33 is detected
by controller 58 by periodically closing battery 6V monitor switch 68 and
battery 12V monitor switch 74 to obtain voltage readings for the
batteries in the first and second battery compartments 28, 30 to
determine their state of charge and estimated remaining life.

[0030] While power is being supplied to BBU output 16 by batteries 33,
controller 58 continues to monitor the signal on mains in line 65 to
determine when the voltage on first path 38 returns to a high level
indicating that power is again being supplied from BBU input 12. A
predetermined time after the voltage on first path 38 returns to an
operating level, controller 58 opens battery path enable switch 48 to
disconnect the batteries 33 in the first and second battery compartments
28, 30 from first path 38. Generally, battery path enable switch 48 is
only opened after a delay, such as 30 seconds, to help avoid repeated
switching of the BBU 10 in the event of transient power events, so that
battery path enable switch 48 is not opened until it reasonably certain
that power supply 14 is again able to reliably supply DC power to the NIU
18 via the BBU 10. This may also help prevent an oscillating condition
that might occur if the mains in voltage level at the mains in pin 13 is
approximately equal to the switchover voltage.

[0031] The first, second and third visual indicators 34a, 34b, 34c may be
illuminated in various combinations to provide information such as
whether DC power is being provided by power supply 14 or batteries 33 and
information on the charge state of the batteries 33, such as "fully
charged", "partially discharged", and "end of life" or "fully
discharged." For example, the visual indicators may be illuminated by
controller 58 as follows, where first visual indicator 34a corresponds to
the below "green" LED, second visual indicator 34b corresponds to the
below "yellow" LED and third visual indicator 34c corresponds to the
below "red" LED:

[0034] 3. Yellow--Main power, batteries have between 3 hours and 6 hours
of back-up time left;

[0035] 4. Yellow Blinking (1 second every 30 seconds)--Battery backup
mode, battery has between 3 and 6 hours of back-up time left;

[0036] 5. Red--Main power, battery needs to be replaced. BBU will sound a
"chirp" once every 30 seconds (similar to a reminder beep of a smoke
detector when battery is exhausted);

[0037] 6. Red Blinking (1 second every 30 seconds)--Battery backup mode,
battery has less than 3 hours of time left. BBU will sound a "chirp" once
every 30 seconds (similar to a reminder beep of a smoke detector when
battery is exhausted; and

[0038] 7. Red Blinking (1 second "on" 1 second "off")--Battery missing or
incorrectly installed (and sufficient power is present to allow the LED's
to be illuminated).

[0039] If the batteries 33 are depleted to the point where loss of back-up
power is imminent, the controller 58 will indicate this condition on the
Light Emitting Diode status display, and will also provide an audible
alarm via buzzer 92 to alert nearby users of this critical condition.
This status information continues to be provided until the batteries 33
are exhausted or replaced by a user.

[0040] The BBU also has a battery "Test" mode which evaluates the amount
of power left in the battery by displaying a "Red-Yellow-Green" power
survey. This is activated by the user through a button (not illustrated)
on the face plate of the BBU body. When powered from an AC source, no
battery power will actually be used to make this evaluation. The
batteries are "sensed" and a status of battery health is displayed for a
15 second interval, after which the BBU returns to "normal" mode. This
gives the user a more detailed evaluation of the battery condition.

[0041] By not requiring the BBU 10 to charge batteries, as is commonly
done with other backup power supplies, the circuitry required for
charging and the associated complexities are eliminated and costs are
reduced. As a consequence, no specialized battery charging circuitry or
thermal management circuitry is necessary in BBU 10. As new primary cell
technology becomes available, new types of batteries can be substituted
directly into the first and second battery compartments 28, 30 without
modifying the BBU 10. In addition, by designing around standard cells,
there is no need for a custom battery pack or connector. An end user can
simply procure standard batteries from any local retail shop and use them
in the BBU 10. A customer is also likely to have spare batteries
available. Another benefit of this approach is that as battery
technologies change, the technology can be used in the BBU as long as the
batteries are within the BBU's operating voltage. In addition, a customer
can still use physically compatible rechargeable batteries in the BBU,
but the customer will be responsible for charging those batteries with a
conventional battery charger.

[0042] The present invention has been described herein in terms of a
presently preferred embodiment. However, additions and changes to this
embodiment will become apparent to those of ordinary skill in the
relevant arts upon a reading of the foregoing description. It is intended
that all such changes and additions comprise a part of the present
invention to the extent they fall within the scope of the several claims
appended hereto.